1. Field of the Invention
This invention relates to the improvement on a single-head plug or a multi-polar coaxial plug being of a type, in which the first pole acting as an internal pole is mounted to the end of an axial rod-like body formed by a metal material, and metal rings of the second to nth poles acting as external poles are mounted around the body in axially parallel arrangement.
2. Description of the Prior Art
The multi-polar coaxial plug of the above type, more specifically, a triple-polar coaxial plug is assembled as follows. As shown in FIGS. 1 and 2, for instance, a rearward-extending center pin 10 formed by a metal material is mounted to the axial center of the rear end of a head 1 formed by a metal material acting as the first pole. An outer sleeve 2 formed by a metal material acting as the second pole is fitted to the circumference of the center pin 10 in coaxial arrangement. A metal ring 3 setting up the third pole is inserted between the outer sleeve 2 and the head 1. An intermediate sleeve 4 formed by a metal material and smaller in diameter than the outer sleeve 2 is inserted between the inner surface of the outer sleeve 2 and the outer surface of the center pin 10 in coaxial arrangement relative to the center pin 10. The front end of the intermediate sleeve is united or connected integrally with the above metal ring 3 setting up the third pole, and a connection screw s separately molded with a resin material for screwing a knob is mounted to the rear end of the above outer sleeve 2 setting up the second pole. Then, the above members are set in a mold while being kept in predetermined positions. Subsequently, a resin material p serving as an insulating material is injected into the mold to allow the insulation of the internal pole acting as the first pole from the metal ring 3 setting up the third pole and the earth pole and also to mold the above members as one united body with the resin material p, providing the triple-polar coaxial plug as shown in FIG. 1. Then, connection lug pieces 1a, 2a, 3a are mounted to the triple-polar coaxial plug for connection to a cord, as shown by a chain line in FIG. 2. In use, the cord is connected to these connection lug pieces 1a, 2a, 3a by soldering.
In the case of providing more poles for the multi-polar coaxial plug of the above type, that is, making an attempt to assemble a quadruple-polar coaxial plug by providing one more pole for the above triple-polar coaxial plug, another intermediate sleeve is required, in addition to the intermediate sleeve 4 inserted between the center pin 10 and the outer sleeve 2. In this case, there is the need for insertion of another intermediate sleeve between the above intermediate sleeve 4 and the center pin 10 or between the above intermediate sleeve 4 and the outer sleeve 2 for uniting or connecting integrally the front ends of these intermediate sleeves with the metal ring 3 acting as the third pole and one more metal ring required for setting up the fourth pole. Thus, since two intermediate sleeves are placed in the shape of a double shaft between the outer surface of the center pin 10 and the outer sleeve 2, the flow path for the resin material p when injected is limited to degrade the flow of the injected resin material p, resulting in a problem of making it hard to perform molding with the resin material.
In view of the above circumstances, the applicants of the present invention have developed a means of assembling a multi-polar coaxial plug as shown in FIG. 5 by the steps of forming connection terminal pieces 4a, 4b of such a shape as the intermediate sleeve 4 united or connected integrally with the metal ring 3 setting up the third pole in the above triple-polar coaxial plug is divided into a plurality of parts in a circumferential direction, placing these connection terminal pieces 4a, 4b around the center pin 10 in coaxial arrangement as shown in FIG. 4 to unite or connect integrally the metal ring 3 setting up the third pole, a metal ring 5 setting up the fourth pole and a metal ring (not shown) setting up the nth pole (not shown) with the ends of the connection terminal pieces and also to connect the rear ends of the connection terminal pieces 4a, 4b of the divided intermediate sleeve shape with a core line of a cord by soldering, then mounting these connection terminal pieces 4a, 4b . . . between the outer surface of the center pin 10 and the inner surface of the outer sleeve 2 in ring-shaped arrangement at predetermined intervals in the circumferential direction as seen from the longitudinal direction, then setting these members in a mold while keeping these members in this state, and injecting the resin material p into the mold to assemble the multi-polar coaxial plug. This means has been applied as Japanese Patent application No. 11-151392.
When more poles are provided for the multi-polar coaxial plug by means of adapting the intermediate sleeve, which is smaller in diameter than the outer sleeve fitted to the circumference of the center pin extending from the rear end of the head, for the connection terminal piece connected to the metal ring mounted between the front face of the outer sleeve and the head in the manner of inserting the intermediate sleeve between the outer surface of the center pin and the inner surface of the outer sleeve in coaxial arrangement relative to the metal ring mounted between the rear face of the head and the front face of the outer sleeve, the following problem is caused. That is, since the plug is limited as to the outer diameter, and the center pin is also limited as to the outer diameter, the intermediate sleeve mounted in multiple arrangement between the outer sleeve and the center pin narrows the flow path for the resin material in excess to thereby make the molding with the resin material difficult.
On the other hand, when more poles are provided by means of mounting the connection terminal pieces, which are connected to the metal rings required for providing more poles, around the center pin in ring-shaped arrangement as seen from the longitudinal direction in the manner of forming these connection terminal pieces to have such a shape as the intermediate sleeve is divided into a plurality of parts in the circumferential direction, only the substantially single intermediate sleeve mounted between the center pin and the outer sleeve makes it possible to increase the poles up to desired number such as four, five and six poles, and as a result, molding by pressure injection of the resin material may be carried out without difficulties. However, the above means involves such a problem as the connection terminal pieces of such the circumferentially divided intermediate sleeve shape are hard to be set in the mold while being kept at their predetermined positions.
The present invention is provided for dissolving the above problems with the conventional means, and its object is to provide a novel method for facilitating molding by pressure injection of a resin material by, while providing more poles by means of mounting connection terminal pieces connected to metal rings acting as incremental poles in ring-shaped arrangement as seen from the longitudinal direction in the manner of forming these connection terminal pieces to have such a shape as an intermediate sleeve is divided into a plurality of parts in the circumferential direction, allowing a plurality of connection terminal pieces of such the circumferentially divided intermediate sleeve shape to be set in a mold in such a state that the connection terminal pieces are temporarily fixed as being held at predetermined positions together with a center pin and an outer sleeve or the like.
According to the present invention, as a means of attaining the above object, there is provided a method of molding a multi-polar coaxial plug in an assembled state. That is, in a multi-polar coaxial plug molded with a resin material after being assembled by the steps of mounting metal rings setting up the third to nth poles in longitudinally parallel arrangement between the rear face of a front end head acting as the first pole and the front face of an outer sleeve fitted in coaxial arrangement to the circumference of a center pin extending from the rear end of the head to set up the second pole, forming connection terminal pieces united or connected integrally with the metal rings to have such a shape as an intermediate sleeve mounted in coaxial arrangement between the outer surface of the center pin and the inner surface of the outer sleeve is divided into parts in the circumferential direction, and then mounting these connection terminal pieces between the center pin and the outer sleeve in ring-shaped arrangement at predetermined intervals in the circumferential direction, the method of molding the multi-polar coaxial plug in an assembled state comprises the steps of forming a resin molding having a hole in the center to allow the center pin to pass, through holes around the center hole to allow the connection terminal pieces to pass and a fit surface on the circumference to allow the outer sleeve to be fitted, and fitting the center pin, the plurality of connection terminal pieces and the outer sleeve or the like to the center hole, the through holes and the fit surface of the resin molding to assemble the above members into a unit in a temporarily fixed state, before setting the above temporarily fixed members together with the resin molding in a mold for molding with the resin material. There is further provided a multi-polar coaxial plug, which comprises a resin molding formed by a resin material and having a hole in the axial center to allow a center pin extending from the rear end of a head to pass, a fit surface on the circumference to allow an outer sleeve to be fitted, and through holes in radially intermediate portions between the fit surface and the center hole in ring-shaped arrangement at predetermined intervals in the circumferential direction as seen from the rear face to allow a plurality of connection terminal pieces connected to the plurality of metal rings mounted between the front end face of the outer sleeve and the rear end face of the head to pass, wherein the center pin extending from the head, the outer sleeve and the connection terminal pieces are assembled into a unit in the temporarily fixed state by fitting the rear end of the center pin, the inner surface of the outer sleeve and the rear ends of the connection terminal pieces to the resin molding, before being set together with the resin molding in the mold for integral molding with a resin material.
The multi-polar coaxial plug according to the present invention is similar to the prior art already applied by the applicants of the present invention in that the nipple-shaped head united or connected integrally with the center pin at the rear end, the outer sleeve fitted to the circumference of the center pin in coaxial arrangement, the plurality of metal rings fitted to the circumference of the center pin in longitudinally parallel and coaxial arrangement at positions between the front face of the outer sleeve and the rear face of the head and the plurality of connection terminal pieces united or connected integrally with the metal rings are made of the metal material, and that the multi-polar coaxial plug is assembled by setting these members in a mold cavity such that these members occupy predetermined positions, before pressure-injection of a molten resin material through a cross gate provided in the mold for integral molding.
However, according to the present invention, the head, the center pin extending from the head, the outer sleeve, the metal rings and the connection terminal pieces united or integrally connected with the metal rings are assembled into a unit in a temporarily fixed state in the manner of fitting these members to the separately-formed resin molding, before being set in the mold. Then, the temporarily fixed members are set in the mold together with the resin molding to start molding of the temporarily fixed members inclusively of the resin molding by pressure injection of the resin material.
The resin molding for use in the present invention takes the axial rod-like shape to allow the inner surface of the outer sleeve to be fitted to the circumference, and is formed by the resin material in advance so as to have the hole in the longitudinal center to allow the rear end of the center pin extending from the head to pass and the longitudinal through holes in the radially intermediate portions between the center hole and the outer surface of the resin molding in ring-shaped arrangement at predetermined intervals in the circumferential direction as seen from the longitudinal direction to allow the rear ends of the connection terminal pieces to individually pass.
The center pin extending from the rear end of the head and the connection terminal pieces connected to the metal rings preliminarily fitted to the center pin are assembled into a unit in the temporarily fixed state by fitting the rear end of the center pin and the rear ends of the connection terminal pieces into the center hole and the through holes of the resin molding respectively, before being set in the mold.
In this place, the inner surface of the cavity defined in the drag of the mold makes it necessary to have slight step portions, which come in contact with the metal rings fitted in longitudinally parallel arrangement to the circumference of the center pin for axial location of the metal rings, within the range of tolerance for the standard size of the target multi-polar coaxial plug for assembling.
Another step portion coming in contact with a flange portion formed on the outer surface of the outer sleeve for axial location of the outer sleeve is also required for the inner surface of the cavity defined in the drag of the mold, as a matter of course. The inner surface of the outer sleeve also has a step portion for regulating the axial fit depth as of the time when the outer sleeve is fitted to the circumference of the resin molding.
The resin molding is structured to have a flow path, which allows the pressure-injected resin material to flow, between the inner surface of the outer sleeve and the resin molding when the resin molding is fitted in a plugged state to the cavity of the outer sleeve. A cut-out portion axially formed on the outer surface of the resin material is only needed for the flow path.
The through holes formed in the resin molding have different sectional shapes so as to vary the circumferential width, for instance, for preventing the wrong pole from being selected when a core of the cord is connected to the connection terminal piece projecting from the corresponding through hole by soldering. Further, the rear end of each connection terminal piece to be inserted into the corresponding through hole also has a shape suited for only the corresponding through hole.
Further, the resin molding has a reference polarity mark on its rear end side projecting from the outer sleeve rearward for easily identifying that the connection terminal piece projecting from the above corresponding through hole is connected to which of the metal rings mounted in longitudinally parallel arrangement.
The cope of the mold is formed to have the inner surface, which comes in contact with the rear ends of the center pin, the resin molding and the outer sleeve or the like for axial location of these members, when the cope is brought into contact with the drag after the resin molding incorporated with the members in the temporarily fixed state is set in the drag.
According to the multi-polar coaxial plug molded in the assembled state as described above, the connection terminal pieces united or connected integrally with the incremental metal rings mounted between the head and the outer sleeve for providing more poles for the multi-polar coaxial head, as needed, are formed to have the shape as the intermediate sleeve is divided into parts in the circumferential direction. Then, the connection terminal pieces of the above shape are incorporated in the preliminarily formed resin molding in the temporarily fixed state together with the center pin and the outer sleeve, before being set in the mold for molding with the resin material. As a result, the operation of setting the members in the mold is substantially facilitated, and besides, the members may be set with accuracy.
On the other hand, in the case of providing more poles by mounting an external pole of large diameter to the circumference of the outer sleeve, there is the need for mounting the external pole of large diameter after the multi-polar coaxial plug is molded on condition that a fit portion allowing the external pole of large diameter to be fitted is formed by the resin material, which is used for molding, to the circumference of the outer sleeve fitted to the circumference of the resin molding before the members incorporated in the resin molding are set in the mold for molding.